In the first nationally representative study of eating disorders in the United States, researchers have found that their incidence is growing among both men and women, and that binge-eating disorder is even more common than the better known anorexia nervosa and bulimia nervosa.

The nationwide survey of more than 2,900 men and women, published in the Feb. 1 issue of the journal Biological Psychiatry, found that 0.6 percent of the population has anorexia, 1 percent has bulimia and 2.8 percent has a binge-eating disorder.

Lifetime rates of the disorders, the researchers found, are higher in younger age groups, suggesting that the problem is increasingly common. Eating disorders are about twice as common among women as men, the study reports.

Experts not involved in the study called it significant.

"This is probably the best study yet conducted of the frequencies of eating disorders in American households," said Dr. B. Timothy Walsh, director of the eating disorders research unit of the New York State Psychiatric Institute at Columbia University Medical Center.

"It confirms that anorexia nervosa and bulimia are uncommon but serious illnesses, especially among women," Walsh said. "It also finds that many more individuals, especially those with significant obesity, are troubled by binge eating, and underscores the need to better understand this problem."

The survey, partly financed by two pharmaceutical companies, was carried out from 2001 to 2003 among adults 18 and older, and the diagnoses were established using face-to-face interviews.

The three disorders all appear in the current edition of the Diagnostic and Statistical Manual of Mental Disorders, or DSM-IV, though binge eating is not considered a definitive diagnosis like anorexia and bulimia. Rather, it is one of a number of categories requiring further study.

The diagnosis requires that a person eat an excessively large amount of food in a two-hour period at least twice a week for six months, feel a lack of control over the episodes, and experience marked distress regarding the practice.

Marlene B. Schwartz, the director of research and school programs at the Rudd Center for Food Policy and Obesity at Yale, who had no role in the study, said binge-eating disorders were "not a matter of just eating too much every now and then."

"The diagnosis requires the feeling that you can't stop," Schwartz said. "And it's that loss of control that makes it a psychiatric disorder different from someone just overindulging every now and then."

Dr. James I. Hudson, the lead author of the new study, noted that binge eating was associated with obesity, particularly severe obesity.

"This brings in a lot of medical consequences and suggests it's a major health problem," he said. "This information will help us make decisions on public health policy." Hudson is director of the psychiatric epidemiology research program at McLean Hospital and a professor of psychiatry at Harvard.

A diagnosis of anorexia requires a refusal to maintain at least 85 percent of normal weight and a distinctly distorted view of one's weight or body shape. Bulimia is characterized by recurrent episodes of binge eating at least twice a week for three months and then compensating for the behavior, usually by self-induced vomiting or abuse of laxatives and other medicines.

Eating disorders, the researchers found, are commonly accompanied by other psychiatric illnesses. In the survey, more than half of people with bulimia also had major depression, 50 percent had phobias and more than one-third had a substance abuse disorder.

Over all, more than 94 percent of people with bulimia, 56 percent of those with anorexia and 79 percent of those with binge-eating disorder had at least one other psychiatric diagnosis.

Hudson said that the most significant limitation of the study was its basis on self-reports, and people tend to underreport their problems with eating disorders. So the true prevalence, he said, is probably higher than that reported.